Correction of fabricated shapes in additive manufacturing

ABSTRACT

A method of fabricating a polishing pad using an additive manufacturing system includes receiving data indicative of a desired shape of the polishing pad to be fabricated by droplet ejection. The desired shape defines a profile including a polishing surface and one or more grooves on the polishing pad. Data indicative of a modified pattern of dispensing feed material is generated to at least partially compensate for distortions of the profile caused by the additive manufacturing system, and a plurality of layers of the feed material are dispensed by droplet ejection in accordance to the modified pattern.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/455,072, filed Mar. 9, 2017, which claims priority to U.S.Provisional Application Ser. No. 62/305,973, filed Mar. 9, 2016, thedisclosures of which are incorporated by reference.

TECHNICAL FIELD

This specification relates to additive manufacturing.

BACKGROUND

An integrated circuit is typically formed on a substrate by thesequential deposition of conductive, semiconductive, or insulativelayers on a silicon wafer. A variety of fabrication processes requireplanarization of a layer on the substrate. For certain applications,e.g., polishing of a metal layer to form vias, plugs, and lines in thetrenches of a patterned layer, an overlying layer is planarized untilthe top surface of a patterned layer is exposed. In other applications,e.g., planarization of a dielectric layer for photolithography, anoverlying layer is polished until a desired thickness remains over theunderlying layer.

Chemical mechanical polishing (CMP) is one accepted method ofplanarization. This planarization method typically requires that thesubstrate be mounted on a carrier head. The exposed surface of thesubstrate is typically placed against a rotating polishing pad. Thecarrier head provides a controllable load on the substrate to push itagainst the polishing pad. A polishing liquid, such as slurry withabrasive particles, is typically supplied to the surface of thepolishing pad.

One objective of a chemical mechanical polishing process is polishinguniformity. If different areas on the substrate are polished atdifferent rates, then it is possible for some areas of the substrate tohave too much material removed (“overpolishing”) or too little materialremoved (“underpolishing”). In addition to planarization, polishing padscan be used for finishing operations such as buffing.

Polishing pads are typically made by molding, casting or sinteringpolyurethane materials. In the case of molding, the polishing pads canbe made one at a time, e.g., by injection molding. In the case ofcasting, the liquid precursor is cast and cured into a cake, which issubsequently sliced into individual pad pieces. These pad pieces canthen be machined to a final thickness. Grooves can be machined into thepolishing surface, or be formed as part of the injection moldingprocess.

SUMMARY

In one aspect, a method of fabricating a polishing pad using an additivemanufacturing system includes receiving data indicative of a desiredshape of the polishing pad to be fabricated by droplet ejection. Thedesired shape defines a profile including a polishing surface and one ormore grooves on the polishing pad. Data indicative of a modified patternof dispensing feed material is generated to at least partiallycompensate for distortions of the profile caused by the additivemanufacturing system, and a plurality of layers of the feed material aredispensed by droplet ejection in accordance to the modified pattern.

In another aspect, a method of fabricating an object using an additivemanufacturing system includes receiving data indicative of a desiredshape of the object to be fabricated by droplet ejection. The desiredshape defines a profile including a top surface and one or morerecesses. Data indicative of a modified pattern of dispensing feedmaterial is generated to at least partially compensate for distortionsof the profile caused by the additive manufacturing system, and aplurality of layers of the feed material are dispensed by dropletejection in accordance to the modified pattern.

In another aspect, a computer program product, tangibly embodied in acomputer readable medium, includes instructions to cause a processor toreceive data indicative of a desired shape of a polishing pad to befabricated by droplet ejection in an additive manufacturing system. Thedesired shape defines a profile including a polishing surface and one ormore grooves on the polishing pad. Data is generated indicative of amodified pattern of dispensing feed material to at least partiallycompensate for distortions of the profile caused by the additivemanufacturing system, and the additive manufacturing system is caused todispense a plurality of layers of the feed material by droplet ejectionin accordance to the modified pattern.

In another aspect, a computer program product, tangibly embodied in acomputer readable medium, includes instructions to cause a processor toreceive data indicative of a desired shape of an object to be fabricatedby droplet ejection in an additive manufacturing system. The desiredshape defines a profile including a top surface and one or morerecesses. Data is generated indicative of a modified pattern ofdispensing feed material to at least partially compensate fordistortions of the profile caused by the additive manufacturing system,and the additive manufacturing system is caused to dispense a pluralityof layers of the feed material by droplet ejection in accordance to themodified pattern.

In another aspect, an additive manufacturing system includes a platformto hold a polishing pad being fabricated, a printhead to form aplurality of layer by ejecting droplets onto the platform or apreviously deposited layer of the polishing pad, and a controllerconfigured to receive data indicative of a desired shape of thepolishing pad, the desired shape defining a profile including apolishing surface and one or more grooves on the polishing pad, generatedata indicative of a modified pattern of dispensing feed material to atleast partially compensate for distortions of the profile caused by theadditive manufacturing system, and cause the printhead to dispense aplurality of layers of the feed material by droplet ejection inaccordance to the modified pattern.

In another aspect, an additive manufacturing system includes a platformto hold a polishing pad being fabricated, a printhead to form aplurality of layer by ejecting droplets onto the platform or apreviously deposited layer of the polishing pad, and a controllerconfigured to receive data indicative of a desired shape of thepolishing pad, the desired shape defining a profile including apolishing surface and one or more grooves on the polishing pad, generatedata indicative of a modified pattern of dispensing feed material to atleast partially compensate for distortions of the profile caused by theadditive manufacturing system, and cause the printhead to dispense aplurality of layers of the feed material by droplet ejection inaccordance to the modified pattern.

Implementations may include one or more of the following features.

The one or more grooves on the polishing pad may be defined by a sidewall substantially perpendicular to the plurality of layers. Thedistortions of the one or more grooves may include distortions of aperpendicularity of the side wall to the polishing surface.

The polishing surface may be substantially parallel to the plurality oflayers. The modified pattern may be configured to at least partiallycompensate for distortions of the polishing surface of the polishing padcaused by the additive manufacturing system. The distortions of thepolishing surface of the polishing pad may include distortions of aplanarity of the polishing surface.

The data indicative of the desired shape of the polishing pad mayinclude data indicative of a pattern of dispensing a plurality of layersof feed material, the data indicative of the pattern including datarepresenting a planar top surface. The data indicative of the modifiedpattern may include data representing a concave top surface generatedbased on the data representing the planar top surface. The datarepresenting the concave top surface may be generated to at leastpartially compensate for distortions of a planarity of a polishingsurface of the polishing pad formed using the data indicative of thepattern.

Generating the data indicative of the modified pattern may includemodifying data indicative of an original pattern to form the desiredshape of the polishing pad. The data indicative of the original patternmay be modified based on a correction profile to the original pattern.The correction profile may include a portion extending beyond a width ofthe original pattern. The correction profile may be determined byidentifying a difference between an original shape and the desiredshape, the original shape being defined at least in part by thedistortions. Modifying the data indicative of the original pattern mayinclude modifying an amount of the feed material deposited per voxel.

The polishing surface may include a partition separating at least twogrooves, and modifying the data indicative of the original pattern mayinclude determining a first volume of material dispensed proximate anedge portion of the partition adjacent the groove, determining a secondvolume of material dispensed in a central portion of the partition, andmodifying a distribution of volume of the feed material based on thefirst volume and the second volume such that the second volume isgreater than the first volume.

The distortions of the profile caused by the additive manufacturingapparatus may include distortions caused by flow of ejected droplets onfeatures being fabricated. The distortions of the profile may includedistortions of a height of the one or more grooves. The desired shape ofthe polishing pad include a planar surface defining the polishingsurface, and the modified pattern may include a nonplanar portioncorresponding to the planar surface. The nonplanar portion may beconfigured to at least partially compensate for distortions of thepolishing surface caused by the additive manufacturing system.

Advantages of the foregoing may include, but are not limited to, thefollowing. The geometry of a polishing pad can be more preciselycontrolled, thereby improving polishing efficacy of the polishing pad.Furthermore, a correction profile can compensate for potentialdistortions by adjusting data that the additive manufacturing apparatususes to form an article, e.g., a polishing pad, rather than removingmaterial after the article has been initially formed. The amount ofpost-processing of the article after it is formed by the additivemanufacturing apparatus can be decreased. As a result, an amount of feedmaterial waste can be reduced, and yield and throughput can beincreased.

The details of one or more implementations of the subject matterdescribed in this specification are set forth in the accompanyingdrawings and the description below. Other potential features, aspects,and advantages will become apparent from the description, the drawings,and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view of a polishing system.

FIG. 2 is a schematic side view of an additive manufacturing apparatus.

FIG. 3A is a top view of an example of a polishing pad.

FIG. 3B is a side view of the polishing pad of FIG. 3A.

FIG. 4 is a flowchart of a process to form an article.

FIG. 5 illustrates an example of an actual shape formed based on adesired shape.

FIG. 6 illustrates an actual shape formed based on modification of thedesired shape of FIG. 5.

FIG. 7 illustrates another example of an actual shape formed based on adesired shape.

FIGS. 8A-8C are bitmap representations of patterns of feed material tobe dispensed.

FIG. 9 illustrates resulting shapes formed using the bitmaprepresentations of FIGS. 8A-8C.

FIG. 10 depicts a process of generating data indicative of a modifiedshape.

FIG. 11 is an example of a bitmap representation of a pattern of feedmaterial to be dispensed in which an order of layers of feed material tobe dispensed has been adjusted.

FIG. 12 is an example of a bitmap representation of a pattern of feedmaterial to be dispensed in which a portion of the bitmap representationextends beyond an original width of a desired shape to be formed.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

An additive manufacturing apparatus can be used to form a polishing pad.The additive manufacturing apparatus can be provided with an initialpattern to dispense feed material. The initial pattern corresponds to adesired shape of the polishing pad to be formed. When the polishing padis formed by the additive manufacturing apparatus using the initialpattern, an actual shape of the polishing pad may include distortionsrelative to the desired shape of the polishing pad. As described herein,the initial pattern provided to the additive manufacturing apparatus canbe modified by a correction profile to generate a modified pattern to atleast partially compensate for these distortions. The resulting shapeformed using the modified pattern can thus more closely match thedesired shape of the polishing pad.

Turning now to FIG. 1, a polishing system 100 includes a polishing pad102 that can be used to polish one or more substrates 104. A descriptionof a suitable polishing apparatus can be found in U.S. Pat. No.5,738,574, the entire disclosure of which is incorporated herein byreference. The polishing system 100 can include a rotatable platen 106on which the polishing pad 102 is placed. During a polishing step, apolishing liquid 108, e.g., abrasive slurry, can be supplied to apolishing surface 103 of polishing pad 102 by a slurry supply port orcombined slurry/rinse arm 110. The polishing liquid 108 can containabrasive particles, a pH adjuster, or chemically active components.

The substrate 104 is held against the polishing pad 102 by a carrierhead 112. The carrier head 112 is suspended from a support structure,such as a carousel, and is connected by a carrier drive shaft 114 to acarrier head rotation motor so that the carrier head can rotate about anaxis 116. The relative motion of the polishing pad 102 and the substrate104 in the presence of the polishing liquid 108 results in polishing ofthe substrate 104.

Referring to FIG. 2, in some examples, an additive manufacturingapparatus 120 that dispenses successive layers of feed material can beused to form the polishing pad 102. Referring to FIGS. 1 and 2, theadditive manufacturing apparatus 120 is operated to form at least apolishing layer 122 of the polishing pad 102. In the manufacturingprocess, thin layers of feed material are progressively dispensed andcured. For example, droplets 124 of feed material, e.g., polishing padprecursor material, can be ejected from a nozzle 126 of a dispenser 128,e.g., a droplet ejector printer, to form a layer 130 of the feedmaterial. The dispenser 128 is similar to an inkjet printer, but usesthe feed material for forming the polishing pad 102 rather than ink.

A controller 129 is operable to control dispensing operations of thedispenser 128 and, if applicable, control curing operations using anenergy source 131 such as a lamp or a laser. The nozzle 126 istranslated (shown by arrow A) across a support 134 to dispense feedmaterial at any portion of a build area on the support 134.

In some implementations, the energy source 131 trails the nozzle 126 asthe nozzle 126 is translated across the support 134, such that feedmaterial dispensed through the nozzle 126 can be immediately cured. Insome implementations, the energy source 131 leads the nozzle 126 as thenozzle 126 is translated across the support 134 in a first scanningdirection while dispensing feed material. The energy source 131 can curethis dispensed feed material as the energy source 131 is scanned acrossthe support 134, e.g., in a second scanning direction opposite the firstscanning direction, thereby providing the feed material additional timeto reach a stable state before being exposed to radiation of the energysource 131. In some implementations, the energy source 131 leads thenozzle 126 as the nozzle 126 is translated across the support 134 in afirst scanning direction, and the energy source 131 is used to cure thedispensed feed material as the energy source is scanned in the firstscanning direction. Thus, the previously dispensed layer of feedmaterial can be cured almost immediately before another layer isdispensed through the nozzle 126. In some implementations, there aremultiple energy sources, with an energy source 131 trails the nozzle 126and an energy source 131 that leads the nozzle 126.

For a first layer 130 a deposited, the nozzle 126 can eject the feedmaterial onto the support 134. For subsequently deposited layers 130 b,the nozzle 126 can eject onto already solidified feed material 132.After each layer 130 is solidified, a new layer is then deposited overthe previously deposited layer until the full 3-dimensional polishinglayer 122 is fabricated. Each layer is applied by the nozzle 126 in apattern stored in a 3D drawing computer program that runs on a computer60. Each layer 130 is less than 50% of the total thickness of thepolishing layer 122, e.g., less than 10%, e.g., less than 5%, e.g., lessthan 1%.

The polishing layer 122 can be formed on a support 134. In someexamples, the support 134 includes a rigid base, or includes a flexiblefilm, e.g., a layer of polytetrafluoroethylene (PTFE). If the support134 includes a flexible film, then the support 134 forms a portion ofthe polishing pad 102. For example, the support 134 can include abacking layer 136 (shown in FIG. 1) of the polishing pad 102 or a layerbetween the backing layer and the polishing layer 122. If the support134 includes the backing layer 136 of the polishing pad 102, the support134 is not removed from the polishing pad 102 after manufacturing of thepolishing pad 102 is complete. Referring to FIG. 1, the polishing pad102 is mounted to the polishing system 100 with the backing layer 136(e.g., the support 134) facing the rotatable platen 106. Alternatively,if the support 134 does not include the backing layer 136 of thepolishing pad 102, the polishing layer 122 can be removed from thesupport 134 after manufacturing of the polishing pad 102 is complete.

Solidification of the layers 130 of feed material can be accomplished bypolymerization. For example, the layer 130 of feed material can be amonomer, and the monomer can be polymerized in-situ by ultraviolet (UV)curing. The feed material can be cured effectively immediately upondeposition, or an entire layer 130 of pad precursor material can bedeposited and then the entire layer 130 be cured simultaneously.Alternatively, the droplets 124 can be a polymer melt that solidifiesupon cooling. In further implementations, the apparatus 120 creates thepolishing layer 122 by spreading a layer of powder and ejecting dropletsof a binder material onto the layer of powder. In this case, the powdercould include additives, e.g., abrasive particles.

In some implementations, the backing layer 136 can also be fabricated bya 3D printing process. For example, the backing layer 136 and polishinglayer 122 could be fabricated in an uninterrupted operation by theapparatus 120. The backing layer 136 can be provided with a differenthardness than the polishing layer 122 by using a different amount ofcuring, e.g., a different intensity of UV radiation, or by using adifferent material. In other implementations, the backing layer 136 isfabricated by a conventional process and then secured to the polishinglayer 122. For example, the polishing layer 122 can be secured to thebacking layer 136 by a thin adhesive layer, e.g., as apressure-sensitive adhesive.

In some implementations, referring to FIGS. 2, 3A, and 3B, when thepolishing layer 122 is formed, the apparatus 120 can selectivelydispense and/or selectively cure portions of the feed material to formgrooves 138 in the polishing layer 122. The grooves 138 can carry thepolishing liquid 108 (shown in FIG. 1). The grooves 138 may be of nearlyany pattern, such as concentric circles, straight lines, cross-hatching,spirals, and the like. Assuming grooves are present, partitions 140between the grooves 138 define the polishing surface 103. The polishingsurface 103, e.g., including the partitions 140 between the grooves 138,can be about 25-90%, e.g., 70-90%, of the total horizontal surface areaof the polishing pad 102. Thus, the grooves 138 can occupy 10%-75%,e.g., 10-30%, of the total horizontal surface area of the polishing pad102. The partitions between the grooves 138 can have a lateral width ofabout 0.1 to 2.5 mm.

Referring to examples illustrated in FIGS. 3A and 3B, in someimplementations, the grooves 138 include concentric circular grooves.These grooves 138 can be uniformly spaced with a pitch P. The pitch P isthe radial distance between adjacent grooves 138. The partitions 140between the grooves 138 have a width W_(p). Each groove 138 are definedby side walls 142 extending from a bottom surface 144 of the groove 138and terminate in at the polishing surface 103, e.g., at the partition140. Each groove 138 may have a depth D_(g) and a width W_(g).

The side walls 142 can extend downwardly from and be generallyperpendicular to the polishing surface 103. In this regard, the sidewalls are substantially perpendicular to the layers 130 of feed materialdispensed on the support 134. In addition, the partitions 140 extendsubstantially parallel to the layers 130 of feed material dispensed onthe support 134.

Each polishing cycle results in wear of polishing pad 102, generally inthe form of thinning of the polishing pad 102 as the polishing surface103 is worn down. The width W_(g) of a groove with substantiallyperpendicular side walls 142 does not change as the polishing pad isworn. Thus, the generally perpendicular side walls 142 ensure that thepolishing pad 102 has a substantially uniform surface area over itsoperating lifetime. As described herein, the manufacturing process toform the polishing pad 102 can include compensatory operations toprevent the polishing surface 103 from being nonplanar, e.g., to ensureplanarity or flatness of the polishing surface 103, and to fabricate theside walls 142 as perpendicular to the polishing surface 103.

The grooves 138 can have a minimum width W_(g) of about 0.34 mm. Eachgroove 138 can have a width W_(g) between 0.34 mm and 2.71 mm, e.g.,between about 0.38 mm and 1.02 mm. Specifically, the grooves 138 mayhave a width W_(g) of approximately 0.51 mm or 0.68 mm. The pitch Pbetween the grooves 138 may be between about 0.68 and 6.10 mm, e.g.,between about 2.29 mm and 5.40 mm. Specifically, the pitch may beapproximately 2.03 or 3.05 mm. Each partition 140 between the grooves138 may have a width W_(p) of at least 0.34 mm. The ratio of groovewidth W_(g) to partition width W_(p) may be selected to be between about0.10 and 0.4. The ratio may be approximately 0.2 or 0.3.

In some implementations, if the polishing pad 102 includes the backinglayer 136, the grooves 138 can extend entirely through the polishinglayer 122. In some implementations, the grooves 138 can extend throughabout 20-80%, e.g., 40%, of the thickness of the polishing layer 122.The depth D_(g) of the grooves 138 can be 0.25 to 1 mm. The polishinglayer 122 can have a thickness T between about 1 mm and 3 mm. Thethickness T should be selected so that the distance D_(p) between thebottom surface 144 of the groove 138 and the backing layer 136 isbetween about 0.5 mm and 4 mm. Specifically, the distance D_(p) may beabout 1 or 2 mm.

Referring to FIG. 4, a manufacturing process 200 to form the polishingpad 102 is illustrated. For example, the additive manufacturingapparatus 120, including the controller 129, can perform the operationsof the manufacturing process 200.

At operation 202, data indicative of a desired shape of the polishingpad 102 to be fabricated is received. Data indicative of shapes,including the data indicative of the desired shape, can be defined by atwo-dimensional or three-dimensional bitmap. In some implementations,the shape data includes data representing a computer-aided design (CAD)model. For example, if the shape data corresponds to the data indicativeof the desired shape, the CAD model is representative of the polishingpad 102 to be fabricated.

In some examples, referring to FIG. 5, the desired shape includes adesired feature 300. Absent further manipulation of the data indicativeof the desired shape, when the additive manufacturing apparatus 120forms the desired shape, e.g., dispenses the feed material and cures orallows the feed material to cure to form the desired shape, an actualfeature 310 may be formed based on the data indicative of the desiredshape including the desired feature 300. For example, to form therectangular desired feature 300, the dispenser 128 is controlled todispense parallel layers 130 of feed material. For each layer, aselected portion of feed material having a uniform width correspondingto a width of the rectangular desired feature 300 is cured.

During this dispensing and curing process, material properties andresolution of the additive manufacturing apparatus 120 can cause edgesof the actual feature 310 to become undesirably rounded or beveled. Inparticular, if the layers 130 of feed material are dispensed inaccordance to an original pattern determined based on the dataindicative of the desired shape, the resulting shape includes roundingor beveling as depicted with respect to the actual feature 310. As shownin FIG. 5, while a top surface 302 of the desired feature 300 is planar,a corresponding top surface 312 of the actual feature 310 is nonplanar.Due to a beveling effect on the top surface 312, lateral edges 304 a,304 b of the desired feature 300 have a greater length than actuallateral edges 314 a, 314 b of the actual feature formed by the additivemanufacturing apparatus 120. The desired feature 300 can correspond tothe partitions 140 between the grooves 138 (shown in FIGS. 3A and 3B).In this regard, the rounding or beveling effect on the top surface 312can cause the polishing surface 103 defined by the partitions 140 tobecome nonplanar. Without being limited to any particular theory, theliquid droplets of feed material ejected onto the previously depositedlayer, e.g., the liquid pad precursor material, can spread and run downthe sides of the feature 300, e.g., due to wetting, resulting in therounding.

To reduce the rounding or beveling effect, the data indicative of thedesired shape can be modified. In this regard, referring back to FIG. 4,at operation 204, data indicative of a modified pattern of dispensingfeed material to compensate for polishing pad distortions is generatedor received. The distortions include distortions of the polishingsurface 103 of the polishing pad 102. These distortions, in some cases,are caused by the additive manufacturing apparatus 120, as describedherein. The modified pattern differs from the original pattern ofdispensing the feed material in that the modified pattern accounts forthe distortions in the actual feature 310 relative to the desiredfeature. In this regard, in some implementations, the data indicative ofthe modified pattern is determined based on relative differences betweenthe actual feature 310 and the desired feature 300.

For example, as shown in FIG. 6, the data indicative of the modifiedshape includes data indicative of a modified feature 320. Even thoughthe top surface 302 of the desired feature 300 is planar, a top surface322 of the modified feature 320 is nonplanar to compensate for thedistortions of the top surface 312 of the actual feature 310 formed fromthe original pattern. The modified feature 320 is determined based onrelative differences between the desired feature 300 and the actualfeature 310. The top surface 322 of the modified feature 320 is concaveto compensate for the convexity of the top surface 312 of the actualfeature 310. In this regard, the data indicative of the modified shapeis determined based on a combination of the data indicative of thedesired shape and data indicative of the actual shape formed using theoriginal pattern.

Referring back to FIG. 4, at operation 206, layers 130 of the feedmaterial are dispensed by droplet ejection in accordance to a modifiedpattern. A resulting actual feature 330 is formed based on dataindicative of the modified pattern to dispense the feed material, themodified pattern being determined based on the data indicative of themodified shape.

When the dispenser 128 is controlled to dispense the layers 130 of feedmaterial in accordance to the data indicative of the modified pattern, asize and shape of a selected portion of the layers 130 of feed materialthat is cured can vary through a height of the feature. This is incontrast to the process to form the actual feature 310 in which theselected portion of cured feed material is consistent from layer tolayer because the width of the desired feature 300 is consistent fromlayer to layer. The modified feature 320 includes a concave portion 326having a width that varies from layer to layer. A modified pattern todispense the feed material to form the concave portion 326 differs fromthe corresponding portion of the original pattern to form the topportion of the desired feature 300 in that the selected cured portionsof the layers 130 of feed material for the modified pattern have varyingwidths and shapes. These varying widths and shapes compensate for thedistortions present in the actual feature 310 such that the resultingactual feature 330 formed using the modified pattern has reducedconvexity compared to the actual feature 310 formed using the originalpattern. For example, a top surface 332 of the actual feature 330 hasincreased planarity and flatness compared to the top surface 312 of theactual feature 310. By intentionally controlling where feed material isbeing dispensed and cured, this correction defined by the modifiedpattern can better match the shape of the resulting polishing pad 102 tothe original desired shape for the polishing pad 102.

For example, the controller 129 can receive a data object, e.g., acomputer aided design (CAD)-compatible file that specifies the initialor intended bitmap. The data object can be stored on a non-transitorycomputer readable medium. The controller 129 can be programmed togenerate a modified bitmap, based on the desired bitmap, that includes afeature to reduce rounding or beveling. Thus, when the polishing pad 102is fabricated using the modified bitmap, it more closely matches thedesired design.

FIG. 7 illustrates another example of a desired feature 400 and anactual feature 410 formed based on dispensing and curing patternsdetermined in accordance to the data indicative of the desired feature400. In this particular example, the desired feature 400 had a width of680 μm and a height of 500 μm, although other dimensions are appropriatein an implemented process. As illustrated, the actual feature 410 had anon-planar top surface and slanted side walls.

The desired feature 400 is a constant width feature, e.g., the partition140 separating the grooves 138 of the polishing pad 102. A constantwidth of the partitions 140 can improve wafer-to-wafer polishinguniformity. Furthermore, the polishing efficacy of the polishing pad 102can be dependent on planarity of the polishing surface 103. Using theprocesses described herein, data indicative of a modified pattern can begenerated so that the resulting actual feature formed using the modifiedpattern more closely matches the desired feature 400. In particular, themodified pattern corresponds to the original pattern with an additionalcorrection profile determined using processes described herein. Theadditional correction profile compensates for the distortions of theactual feature 410 formed using the original pattern.

The examples of FIGS. 8A-8C are representative of data indicative ofshapes used by the additive manufacturing apparatus 120 to dispense andcure the feed material. In some implementations, the data indicative ofthe shapes described herein include bitmap representations of the shapesto be formed or the shapes formed. Each bit of the bitmap can correspondto a voxel of a feature of the polishing pad 102 to be formed. Forexample, FIG. 8A illustrates a bitmap representation 500 generated basedon the desired feature 400. FIG. 8B and FIG. 8C illustrate bitmaprepresentations 502, 504 generated to compensate for distortions of theactual feature 410. The bitmap representations 502, 504 are thusrepresentative of modified features generated based on the desiredfeature 400 and the actual feature 410. The bitmap representations 502,504 include stepped portions 506, 508 to approximate concavities of themodified features that compensate for the convexity of the actualfeature 410. The concavity approximated by the stepped portions 506 isless than the concavity approximated by the stepped portions 508.

FIG. 9 illustrates resulting actual features 510, 512, 514 formed usingmodified patterns generally corresponding to the bitmap representations500, 502, 504, respectively. The actual features 510, 512, 514 includevariable width portions 516, 518, 520, respectively, with the variablewidth portion of the actual feature 510 having the greatest height. Thevariable width portion 518 has a height larger than the variable widthportion 520. Thus, a constant width can be more readily achieved throughthe bitmap representations 502, 504 that include non-constant widthpatterns that compensate for distortions of the actual feature 510formed using the bitmap representation 500.

FIG. 10 illustrates an example process of determining a modifiedfeature, and hence determining a modified pattern with which to dispensefeed material to form a feature that better matches a desired feature.An actual shape is formed based on data representing a desired shape600, e.g., using the additive manufacturing apparatus 120 as describedherein, and then data representing a measured shape 602 of the actualshape is determined. The data representing the measured shape 602 can bedetermined using, for example, a confocal laser microscope to measurethe height profile of the actual shape. Data representing a difference604 between the measured shape 602 and the desired shape 600 is thendetermined. The difference 604 can be indicative of the distortion ofthe measured shape 602 relative to the desired shape 600 and/or thedistortion of the actual shape relative to the desired shape 600. Thedifference 604 can correspond to the measured shape 602 being subtractedfrom the desired shape 600. The data representing the difference 604represents, for example, the portion of the measured shape 602 that doesnot match with the desired shape 600.

Data representing an inverted difference 606 is determined based on thedata representing the difference 604. The data representing the inverteddifference 606 is complementary to the difference 604, therebycompensating for the distortion of the measured shape 602. In someimplementations, the inverted difference can be scaled anywhere from 1to 3 times to form the data representing the inverted difference 606.The inverted difference 606 corresponds to the correction profile usedto modify the original desired shape 600. In this regard, the datarepresenting the inverted difference 606 is added to the datarepresenting the desired shape 600 to form data representing a modifiedshape 608. The data described in this example can correspond to bitmaps,as described herein.

The controller, e.g., the controller 129, can be implemented in digitalelectronic circuitry, or in computer software, firmware, or hardware, orin combinations of them. The controller can include one or more computerprogram products, i.e., one or more computer programs tangibly embodiedin an information carrier, e.g., in a non-transitory machine readablestorage medium or in a propagated signal, for execution by, or tocontrol the operation of, data processing apparatus, e.g., aprogrammable processor, a computer, or multiple processors or computers.A computer program (also known as a program, software, softwareapplication, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, and it can bedeployed in any form, including as a standalone program or as a module,component, subroutine, or other unit suitable for use in a computingenvironment. A computer program can be deployed to be executed on onecomputer or on multiple computers at one site or distributed acrossmultiple sites and interconnected by a communication network. Theprocesses and logic flows described in this specification can beperformed by one or more programmable processors executing one or morecomputer programs to perform functions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application specific integrated circuit).

The controller 129 and other computing devices part of systems describedcan include non-transitory computer readable medium to store a dataobject, e.g., a computer aided design (CAD)-compatible file thatidentifies the pattern in which the feed material should be formed foreach layer. For example, the data object could be a STL-formatted file,a 3D Manufacturing Format (3MF) file, or an Additive Manufacturing FileFormat (AMF) file. For example, the controller could receive the dataobject from a remote computer. A processor in the controller 129, e.g.,as controlled by firmware or software, can interpret the data objectreceived from the computer to generate the set of signals necessary tocontrol the components of the additive manufacturing apparatus 120 todeposit and/or cure each layer in the desired pattern.

A number of implementations have been described. Nevertheless, it willbe understood that various modifications may be made.

In some implementations, referring to FIG. 12, the correction profileincludes portion extending beyond a width of the originally desiredfeature. A modified bitmap representation 800 includes a protrudingportion 802 extending beyond a width of the bitmap representation 500 ofthe desired feature. The protruding portion 802 is dispensed, forexample, with the uppermost layers of feed material. The layers of feedmaterial underlying the uppermost layers of feed material may experiencewidening due to material roll off during dispensing. As a result,referring briefly to FIG. 7, the underlying layers of feed materialdefine a widened portion 402 that has a width larger than the width ofthe desired feature. The protruding portion 802 can correspond to feedmaterial to be dispensed on top of the widened portion 402 to compensatefor the variable width of the widened portion 402 and improve theconsistency of the width of the feature at the widened portion 402.

The approach shown in FIGS. 8B and 8C is to deposit one or moreadditional layers of feed material to compensate for the height of thefeature being less than desired. For example, one or more additionallayers of feed material can be deposited in regions where rounding orbeveling occurs. However, alternatively or in addition, the amount offeed material deposited in a layer can compensate for the height featurebeing less than desired. For example, the size of droplets or the numberof droplets ejected can be increased for voxels located in regions wherethe height of the feature is less than desired, e.g., where rounding orbeveling occurs.

In some implementations, a distribution of volume of the feed materialis modified depending on a location at which the droplets 124 are to bedispensed. A volume of the droplets 124 of feed material is variedduring the dispensing operation. For example, referring back to FIG. 6,the volume of the droplets 124 for forming edges 322 a, 322 b of thefeature can be less than the volume of droplets 124 for forming theinterior portion 322 c of the feature. The controller 129 determines theappropriate weight for forming the edges 322 a, 322 b and the weight forforming the interior portion 322 c based on the material properties ofthe feed material. The dispenser 128 can dispense less feed material tominimize roll off of the feed material. As the dispenser 128 moves toform the interior portion 322 c of the feature, the volume of dropletsis increased. In some implementations, the volume of the droplets 124define a gradient from the edges 322 a, 322 b to the center of thefeature. Depending on the wetting effect of the feed material, this typeof volume control can be used to modulate an amount of feed materialcured when the energy source 131, if present, is operated. For example,if the energy source 131 is scanned across the support 134 to curedifferent portions of the dispensed feed material, drop volume controlcan allow for less feed material to roll off for each pass of the energysource 131 while injecting more feed material at the edges 322 a, 322 bof the feature to reduce the beveling effect described herein.

In some implementations, multiple types of feed material are dispensed.The additive manufacturing apparatus 120 includes, for example, two ormore dispensers, each dispenser dispensing a different type of feedmaterial. In some cases, a single dispenser, e.g., the dispenser 128,receives multiple types of feed material and dispenses a mixture of themultiple types of feed material. Because properties of a first type offeed material may vary from properties of a second type of feedmaterial, the modification to the original pattern to dispense the firsttype of feed material may include a greater or smaller amount of scalingthan the modification to the original pattern to dispense the secondtype of feed material. Alternatively, if droplet weight is controlled,the weights of the droplets of the first type of feed material can becontrolled to be higher or lower than the weights of the droplets of thesecond type of feed material. In some cases, the size of the droplets ofthe first type of feed material can be controlled to be larger orsmaller than the sizes of the droplets of the second type of feedmaterial.

In some implementations, multiple types of feed material form differentportions of the polishing pad 102, for example, to form the polishinglayer 122 and the backing layer 136, or to form different portions ofthe polishing layer 122, e.g., to provide a polishing layer withpolishing properties that vary laterally across the polishing surface.The second type of feed material can include the first type of feedmaterial with an additive that alters the properties of the second typeof feed material relative to the first type of feed material. Theadditive includes, for example, a surfactant that can adjust propertiesof the uncured feed material, for example, zeta potential,hydrophilicity, etc.

Thickness of each layer of the layers of feed material and size of eachof the voxels may vary from implementation to implementation. In someimplementations, when dispensed on the support 134, each voxel can havea width of, for example, 10 μm to 50 μm (e.g., 10 μm to 30 μm, 20 μm to40 μm, 30 μm to 50 μm, approximately 20 μm, approximately 30 μm, orapproximately 50 μm). Each layer can have a predetermined thickness. Thethickness can be, for example, 1 to 80 μm, e.g., 2 to 40 μm (e.g., 2 μmto 4 μm, 5 μm to 7 μm, 10 μm to 20 μm, 25 μm to 40 μm).

Although the method and apparatus have been described in the context offabrication of a polishing pad, the method and apparatus can be adaptedfor fabrication of other articles by additive manufacturing. In thiscase, rather than a polishing surface, there would simply be a topsurface of the object being fabricated, and there would be recesses inthe top surface. The modified pattern can at least partially compensatefor distortions caused by the additive manufacturing system.

In addition, although the method and apparatus haves been described inthe context of fabrication by droplet ejection, the method apparatus canbe adapted for fabrication by other additive manufacturing techniques,e.g., selective powder dispensing followed by sintering. Accordingly,other implementations are within the scope of the claims.

What is claimed is:
 1. An additive manufacturing system, comprising: aplatform to hold a polishing pad being fabricated; a printhead to form aplurality of successive layers of the polishing pad by ejecting dropletsof polishing pad precursor material onto the platform or a previouslydeposited and cured layer of the polishing pad; a light source to curethe polishing pad precursor material; and a control system configured toreceive data indicative of a desired shape of the polishing pad, thedesired shape defining a profile including a polishing surface and oneor more grooves on the polishing pad, based on data indicative of adesired shape of the polishing pad and data indicative of distortions ofthe profile caused by the additive manufacturing system data, generatedata indicative of a pattern of dispensing droplets of polishing padprecursor material to at least partially compensate for the distortionsof the profile, cause the printhead to dispense a plurality of layers ofthe polishing pad precursor material by droplet ejection in accordanceto the modified pattern, and cause the light source to cure theplurality of layers to form the polishing pad.
 2. The system of claim 1,wherein the control system is configured to apply a correction profileto the desired shape to generate a modified shape, and to generate thedata indicative of the pattern from the modified shape.
 3. The system ofclaim 2, wherein the control system is configured to modify dataindicative of the desired shape using the data indicative of thedistortions to generate data indicative of a distorted shape of thepolishing pad that would occur in absence of the modified pattern. 4.The system of claim 3, wherein the control system is configured todetermine the correction profile by calculating a difference between thedistorted shape and the desired shape.
 5. The system of claim 3, whereinthe control system is configured to cause the printhead to add one ormore additional layers of the polishing pad precursor material tocompensate for a height of a feature in the distorted shape being lessthan a desired height in the desired shape.
 6. The system of claim 3,wherein the control system is configured to cause the printhead toincrease an amount of the polishing pad precursor material deposited pervoxel to compensate for a height of a feature in the distorted shapebeing less than a desired height in the desired shape.
 7. The system ofclaim 1, wherein the control system is configured to detect from thedata indicative of the desired shape a presence in the desired shape ofa partition separating at least two grooves.
 8. The system of claim 7,wherein the control system is configured to determine a first volume ofmaterial dispensed proximate an edge portion of the partition adjacentthe groove, determine a second volume of material dispensed in a centralportion of the partition, and modify a distribution of volume of thefeed material based on the first volume and the second volume such thatthe second volume is greater than the first volume.
 9. A computerprogram product, tangibly embodied in a non-transitory computer readablemedium, comprising instructions to cause a processor to: receive dataindicative of a desired shape of the polishing pad, the desired shapedefining a profile including a polishing surface and one or more grooveson the polishing pad, based on data indicative of a desired shape of thepolishing pad and data indicative of distortions of the profile causedby the additive manufacturing system data, generate data indicative of apattern of dispensing droplets of polishing pad precursor material to atleast partially compensate for the distortions of the profile, and causethe printhead to dispense a plurality of layers of a polishing padprecursor material by droplet ejection in accordance to the modifiedpattern.
 10. The computer program product of claim 9, comprisinginstructions to apply a correction profile to the desired shape togenerate a modified shape, and to generate the data indicative of thepattern from the modified shape.
 11. The computer program product ofclaim 10, comprising instructions to modify data indicative of thedesired shape using the data indicative of the distortions to generatedata indicative of a distorted shape of the polishing pad that wouldoccur in absence of the modified pattern.
 12. The computer programproduct of claim 11, comprising instructions to determine the correctionprofile by calculating a difference between the distorted shape and thedesired shape.
 13. The computer program product of claim 11, comprisinginstructions to cause the printhead to add one or more additional layersof the polishing pad precursor material to compensate for a height of afeature in the distorted shape being less than a desired height in thedesired shape.
 14. The computer program product of claim 11, comprisinginstructions to cause the printhead to increase an amount of thepolishing pad precursor material deposited per voxel to compensate for aheight of a feature in the distorted shape being less than a desiredheight in the desired shape.
 15. A method of fabricating a polishing padusing an additive manufacturing system, the method comprising:receiveing data indicative of a desired shape of the polishing pad, thedesired shape defining a profile including a polishing surface and oneor more grooves on the polishing pad, based on data indicative of adesired shape of the polishing pad and data indicative of distortions ofthe profile caused by the additive manufacturing system data, generatingdata indicative of a pattern of dispensing droplets of polishing padprecursor material to at least partially compensate for the distortionsof the profile, and dispensing a plurality of layers of the polishingpad precursor material by droplet ejection in accordance to the modifiedpattern, and curing the plurality of layers to form the polishing pad.16. The method of claim 15, comprising applying a correction profile tothe desired shape to generate a modified shape, and generating the dataindicative of the pattern from the modified shape.
 17. The method ofclaim 16, comprising modifying data indicative of the desired shapeusing the data indicative of the distortions to generate data indicativeof a distorted shape of the polishing pad that would occur in absence ofthe modified pattern.
 18. The method of claim 17, comprising determiningthe correction profile by calculating a difference between the distortedshape and the desired shape.
 19. The method of claim 17, comprisingadding one or more additional layers of the polishing pad precursormaterial to compensate for a height of a feature in the distorted shapebeing less than a desired height in the desired shape.
 20. The method ofclaim 17, comprising increasing an amount of the polishing pad precursormaterial deposited per voxel to compensate for a height of a feature inthe distorted shape being less than a desired height in the desiredshape.